Base plate for an electric tool and method for manufacturing same

ABSTRACT

In a base plate ( 1 ) for a power tool ( 13 ), in particular for hand-guided circular saws, sabre saws, wall chasers, and routers, comprised of a metal sheet, having reinforcing elements that protrude out from the plane of the metal sheet, at least one of which is embodied in the form of a lateral stop surface ( 12 ), and having attaching elements ( 14 ) that protrude out from the plane of the metal sheet for fastening the base plate ( 1 ) to the miter angle ( 23 ), a more favorable manufacture with a low weight and higher rigidity with simultaneously lower risk of breakage is achieved in that the metal sheet is comprised of light metal and the entire base plate ( 1 ) is embodied in one piece. According to the present invention, a base plate ( 1 ) of this kind is manufactured by means of a stamping and bending process.

PRIOR ART

The invention is based on a base plate for a power tool with thespecies-defining characteristics of claim 1.

Known base plates for hand-guided circular saws, sabre saws, wallchasers, and routers are embodied as flat components with a lowstructural height. They serve to guide the power tool on a work piece.There are three basic embodiment forms of base plate.

The first group of known base plates includes those that are stamped andbent out of sheet steel. They typically have a circumferential collarand longitudinal reinforcing creases that serve to increase rigiditysince the sheet thicknesses lie in a range of only 1.5 to 2.5 mm.Components like this are favorable from a manufacturing standpointbecause among other things, technical functions like accommodation of aparallel cutting guide or pivot points for angle adjustment can beperformed by parts that can be formed directly out of the metal sheet,without requiring subsequent finishing work. Moreover, warped baseplates can also be bent back again. However, such base plates have thedisadvantage of being heavy.

The second group of known base plates includes stamped parts that aremade of light metal and do not have circumferential collars. In order toachieve a sufficient degree of rigidity, sheet thicknesses of 5 to 6 mmare used. However, add-ons are required in order to perform theabove-mentioned technical functions. A base plate of this kind has a lowweight and can also be bent back again when warped. But a base plate ofthis kind is also expensive to manufacture because it must be equippedwith add-ons.

The third group of known base plates includes cast components made oflight metal alloys that do in fact have a very low weight and a highdegree of rigidity, but it is very expensive to manufacture these baseplates because they require subsequent finishing work. Cast componentsof this kind also tend to break under impact.

ADVANTAGES OF THE INVENTION

A base plate for a power tool according to the present invention withthe characteristics of claim 1 has the advantage over the prior art thatusing of a sheet of light metal and a one-piece design of the base platecan result in an advantageous manufacture; the base plate has only a lowweight with a high degree of rigidity, can be bent back again whenwarped, and also does not break under impact. According to the presentinvention, a base plate of this kind is manufactured using a stampingand bending method.

Embodying the sheet with a material thickness of less than 4 mm, inparticular 3 mm, yields a particularly lightweight base plate thatnonetheless has a sufficient degree of rigidity. It is particularlyadvantageous to use a sheet comprised of an aluminum alloy.

Embodying at least one reinforcing element in the form of acircumferential collar yields a base plate with a particularly highdegree of rigidity and a low weight. A particularly favorable degree ofrigidity is achieved if the circumferential collar has a height that isat least twice the material thickness of the sheet.

Embodying at least one reinforcing element in the form of a lateral,diagonal, or longitudinal reinforcing crease increases the rigidity ofthe base plate even further.

Providing an integral embodiment of projections and a threaded dome forguiding and positioning a parallel cutting guide that is integral to thebase plate obviates the need to provide add-ons to the base plate inorder to attach a parallel cutting guide. When connecting elements foran angle adjustment of a saw blade are embodied as integral to the baseplate, it is also unnecessary to provide additional add-ons for pivotingthe cutting plane. Embodying a guide channel as integral to the baseplate makes it possible to place the power tool onto a guide railwithout requiring add-ons to do so. The three measures mentioned aboveeach achieve a reduction in the manufacturing costs of the base plate,which add up to a considerable savings potential when the three measuresare combined.

Because the connecting elements have bores that define a rotation axisfor the angle adjustment of a saw blade, the base plate has theelements-which are required to be able to change the angle of a sawblade-already integrated into it, without requiring other add-ons. Thisallows the base plate to be inexpensively manufactured.

Other advantageous embodiments of the present invention are the subjectof the dependent claims.

DRAWINGS

An exemplary embodiment of the invention will be explained in detail inthe following description in conjunction with the accompanying drawings.

FIG. 1 is a three-dimensional depiction of a hand circular saw,

FIG. 2 is a top view of a base plate according to the present invention(rotated by 180° in relation to the one in FIG. 1), and

FIG. 3 is a three-dimensional depiction of the base plate according tothe present invention shown in FIG. 2.

FIG. 1 shows a power tool 13 in the form of the hand-guided circularsaw. The power tool 13 has a base plate 1 according to the presentinvention to which a motor contained in a motor housing 3 is attached.The motor drives a saw blade 19 located under a guard 2. A handle 4 isused for moving the power tool 13. An adjustable parallel cutting guide5 is attached to the base plate 1. The saw blade 19 is connected to thebase plate 1 so that it can be moved between a plane perpendicular tothe base plate 1 and a sawing plane that is inclined at an angle. Forthis purpose, the base plate 1 is provided with a connecting element 18,which has a pivoting slot 16 and a bore 11 for accommodating the pivotpin (not shown). A pin indirectly connected to the saw blade 19 can beguided in the pivoting slot 16 and can be fixed in its position in thepivoting slot 16 by means of a wing nut 20. The above-mentioned designof the power tool 13 is in principle known from the prior art.

The characteristics of the base plate 1 according to the presentinvention can best be seen in FIGS. 2 and 3 and will be described below.

The base plate 1 is manufactured in one piece out of a sheet of lightmetal by means of a stamping and bending process. By contrast with astamping process, this produces a three-dimensional form of the baseplate 1. The base plate 1 depicted is comprised of an aluminum alloywith a material thickness 15 of 3 mm. A base plate 1 of this kind has aflexural rigidity comparable to that of a steel plate 2 mm thick.However, due to the significantly lower density of the aluminum alloy incomparison to that of steel, the weight has been cut roughly in halfdespite the increase in material thickness.

The favorable rigidity of the base plate 1 according to the presentinvention is achieved by means of a circumferential collar 6. Thecircumferential collar 6 has a height 17 that is roughly twice thematerial thickness 15 of the metal sheet. The inside height is roughly6.5 mm and the outside height is roughly 9 mm. To further increase therigidity of the base plate 1, two longitudinal reinforcing creases 7 areprovided parallel to the orientation of the saw blade 19. This achievesa rigidity within the range of those in alternative embodiment forms.

In addition, the rigidity is further increased by means of an additionalcollar 21 that surrounds an opening 22 for the saw blade 19.

In order to accommodate a device that guides the saw blade 19, twoconnecting elements 18 are incorporated into the base plate 1. Both ofthem protrude perpendicularly up from the plane of the base plate 1. Oneof the two connecting elements 18 is part of the additional collar 21,the other connecting element 18 is part of the circumferential collar 6.Each of the two connecting elements 18 has a bore 11 that supports thepivot pin, which is indirectly connected to the saw blade 19 anddetermines the cutting plane of the saw blade. In addition to the bore11, the connecting element 18 that is part of the circumferential collar6 is also provided with a pivoting slot 16 whose function has alreadybeen explained above in conjunction with FIG. 1.

On its longitudinal sides, i.e. parallel to the saw blade 19, thecircumferential collar 6 is embodied as a stop surface 12. This makes iteasy to guide the power tool 13 along a batten or a similar straightobject.

In order to be able to fasten the parallel cutting guide 5 to the baseplate 1 in various positions, a threaded dome 9 is provided, whichaccommodates a wing nut (not shown) and securely clamps the parallelcutting guide in its position. In order to achieve a clean, parallelguidance of the parallel cutting guide 5, a number of projections 8 areprovided on the base plate 1. Both the projections 8 and the threadeddome 9 here are embodied integral to the base plate 1.

A row of attaching elements 14 is incorporated into the base plate 1 inorder to permit the base plate 1 to be connected to the miter angle 23.The basic connection of the base plate 1 to the miter angle 23 is wellknown from the prior art and is not described in detail since it is notessential to the present invention.

The above explanations regarding the material thickness 15 of the metalsheet and the height 17 of the circumferential collar 6 are merely givenby way of example. It is clear to those skilled in the art that othervalues can also be used without going beyond the scope of the concept ofthe present invention.

In summary, the base plate 1 according to the present invention, whichis manufactured by means of a stamping and bending process according tothe present invention, achieves the advantages of the known base platedesigns, namely those in the form of a stamped and bent component madeof plate steel, a stamped part made of light metal, and a cast componentmade of a light metal alloy, without the disadvantages of the threecomponents mentioned.

Compared to the stamped and bent component made of plate steel, the baseplate 1 according to the present invention has a comparable rigidity,but a significantly reduced weight.

By contrast with stamped components that can only be embodied in twodimensions due to the stamping process, the base plate 1 according tothe present invention has a significantly smaller material thickness 15.In the present case, the material thickness 15 is 3 mm, whereas stampedcomponents typically require material thicknesses 15 of greater than 5mm. This large material thickness 15 is necessary in order to obtain thelateral stop surface 12 that in the present case, is provided by thecircumferential collar 6. In the stamped component, the height 17 of thestop surface is equal to the material thickness 15. With the knownstamped components, it is also necessary to provide additional add-onsfor the geometry accommodating the parallel cutting guide 5 and for theangle adjustment of the saw blade 19. On the one hand, this results in ahigher material consumption and a higher weight and on the other hand,increases the cost of manufacturing the stamped component. The baseplate 1 according to the present invention, however, which is comprisedof a light metal alloy and has been produced by means of a stamping andbending process, is equipped with reinforcing elements that do notrequire the entire base plate 1 to have a greater material thickness 15.In addition, the lateral stop surfaces 12 can be set to the desiredheight 17 independent of the material thickness 15. The requiredmaterial thickness 15 can therefore be reduced in comparison to that ofstamped components while maintaining the same functionality, thusreducing both weight and cost.

A light metal cast component that has a geometry for accommodating theparallel cutting guide can in fact be used as the base plate, but thecast component requires material-removing finishing work. For thisreason, a base plate 1 according to the present invention, which hasbeen manufactured using the stamping and bending process, is lessexpensive because it does not require subsequent machining. Moreover,the base plate according to the present invention has the advantage of agreater ductility than a cast component. Cast metal is more brittle thanmetal that is suited to forming processes. This means that the castcomponent will break significantly more easily under impact than acomponent manufactured out of a rolled metal sheet. After being droppedand warped, the base plate 1 according to the present invention can bebent back into place and is once again ready for use. By contrast, acast component tends to break when dropped. A base plate 1 according tothe present invention matches the weight reduction achieved by thecomponent cast out of light metal, which means that the cast componenthas no advantage over the present invention.

1. A base plate (1) for a power tool (13), in particular for hand-guidedcircular saws, sabre saws, wall chasers, and routers, comprised of ametal sheet, having reinforcing elements that protrude out from theplane of the metal sheet, at least one of which is embodied in the formof a lateral stop surface (12), and having attaching elements (14) thatprotrude out from the plane of the metal sheet and are provided forfastening the base plate (1) to the miter angle (23), wherein the metalsheet is comprised of light metal and the entire base plate (1) isembodied in one piece.
 2. The base plate (1) as recited in claim 1,wherein the material thickness (15) of the metal sheet is less than 4mm, in particular 3 mm.
 3. The base plate (1) as recited in claim 1,wherein the metal sheet is comprised of a light metal alloy, inparticular an aluminum or magnesium alloy.
 4. The base plate (1) asrecited in claim 1, wherein at least one reinforcing element (6, 7) isembodied in the form of a circumferential collar (6).
 5. The base plate(1) as recited in claim 4, wherein the circumferential collar (6) has aheight (17) of at least twice the material thickness (15) of the metalsheet.
 6. The base plate (1) as recited in claim 1, wherein at least onereinforcing element (6, 7) is embodied in the form of a lateral,diagonal, or longitudinal reinforcing crease (7).
 7. The base plate (1)as recited in claim 1, wherein projections (8) and a threaded dome (9)for guiding and positioning a parallel cutting guide (5) and/orconnecting elements (18) for an angle adjustment and/or a guide channel(10) are integrated into the base plate (1).
 8. The base plate (1) asrecited in claim 7, wherein the connecting elements (18) have bores (11)that define a rotation axis for the angle adjustment of a saw blade(19).
 9. A method for manufacturing a base plate (1) as recited in claim1, wherein the method is comprised of a stamping and bending process.